Figure 3
From: Hamiltonian of a flux qubit-LC oscillator circuit in the deep–strong-coupling regime
(a) Numerically calculated energy levels of \(\hat{\mathcal {H}}_{2}\) as functions of \(\Phi _x\). (b) The lowest two energy levels of \(\hat{\mathcal {H}}_{2}\). (c) The expectation values of the flux operator \(\left\langle g \left| \hat{\Phi }_2 \right| g \right\rangle\) and \(\left\langle e \left| \hat{\Phi }_2 \right| e \right\rangle\). In (b,c), the solid circles are obtained from numerical calculations of \(\hat{\mathcal {H}}_{2}\), while the lines are obtained from fitting by \(\hat{\mathcal {H}}_{FQ}\). The black and red colors respectively indicate states \(\left| g\right\rangle\) and \(\left| e\right\rangle\). In the calculation, we used the following parameters: \(L_c + L_2=2050\) pH, \(L_J = 990\) pH (\(E_J/h=165.1\) GHz), and \(C_J=4.84\) fF (\(E_C/h = 4.0\) GHz).
